In the age of information technology, the requirements of communications systems are increasing at a staggering pace. The receiver is a key component in the performance of communication systems. Its function is to receive incoming signals and process the signals so they can be used by other components in the device. Devices such as cell phones, PDAs, mobile televisions, personal navigation devices, personal media players, and a myriad others contain receivers that perform this function. Signals can be conveyed to a receiver via an antenna, through direct wire transmission, and in other ways.
Ideally, a receiver needs to produce a signal of sufficiently high power that contains undistorted desirable components, such as the preferred channel, and none of the undesirable components, such as blockers, adjacent channels, and noise. Generally, signals are optimized for these traits in a portion of the receiver called a tuner. Building a power efficient, inexpensive, and compact tuner that meets industry standards can be extremely challenging for manufacturers.
First, an incoming signal's power may vary significantly and fluctuate rapidly due to, for example, attenuation, variation in distance between the receiver and the transmitter, fading, and the Doppler Effect. Signal power fluctuations may be in the order of several magnitudes. Hence, a tuner must be capable of performing a broad range of amplification while preserving other signal characteristics. Second, the gain of undesired components can be as much as several orders of magnitude larger than the desired signal and can be located near the desirable channel in the frequency range, for instance, in the case of near adjacent channels. Sharp, selective filtering is required to reject such components. In addition, tuners need to perform in a broad frequency range, such as the broadband TV signal range of 50 MHz-1 GHz, while maintaining a high required signal to noise ratio (SNDR), particularly in TV applications. These problems present significant challenges in integration of RF tuners.
To achieve these goals, existing devices employ CAN tuners, which are large and limited in application. Current solid-state tuners are based on external SAW filters, which are expensive, consume a lot of power, and usually are not applied in inexpensive CMOS technology. What is needed is a highly integrated RF tuner that is compact in size, inexpensive to produce, and exhibits low power consumption.